Validate: Script does not exit code 1 when failing to find file

[MattIPv4]

In a recent CI run, it was observed that the validate script output an error message stating it could not find the var declaration in the cnames_active.js, but this did not cause the CI run to fail.

https://github.com/js-org/js.org/runs/8112104112?check_suite_focus=true